Preventing pipe line corrosion



June 11, 1957 P. s. WlLLlAMS 2,795,560 1 PREVENTING PIPE LINE CORROSIONFiled Dec. 51, 1952 PhilLp muiams {brave-a bar 2,795,560 PREVENTlNG PIPELINE CORROSION Philip S. Williams, Tulsa, Okla, assignor to EssoResearch and Engineering Company, a corporation of Delaware ApplicationDecember 31, 1952, Serial No. 328,907

3 Claims. (Cl. 252-387) The present invention is concerned with animproved method for preventing corrosion in pipe lines through whichhydrocarbon products are transported. The invention is more particularlyconcerned with a novel method of placing the inhibitors in the criticalregions in the pipe line or at the points where it is most essential tohave inhibiting substances present. In general, such areas or regionscoincide with those where water accumulates. In accordance with thepresent invention, water soluble, oil insoluble corrosion inhibitingsubstances are added in the form of pellets to the fluid beingtransported through the pipe line. Thus, at points in the line wherewater tends to accumulate and where corrosion occurs, the pellets willbe dissolved in the water layer and thus will materially decrease thecorrosion that would otherwise occur at these points.

It is well known in the art to utilize various corrosion inhibitors aswell as other means for preventing corrosion in pipe lines, storagetanks and the like. It is also known that corrosion is most likely tooccur where water or moisture is present. With respect to thetransportation of petroleum liquids by pipe line, a particular problemexists in that as the pipe line passes over the usual terrain low spotsoccur in the line. It is practically impossible to keep out of apetroleum liquid pipeline system even with refinedproducts since waterwill enter the system wherever there is access to the atmosphere, as instorage tanks, for example. In addition, in the case of crude oils, itis not considered practical or economic to remove all or" the water fromthe oil before transmitting it to the refinery. Hence, since water isusually present as a separate phase in petroleum liquids beingtransported through a pipeline, it will tend to settle out andaccumulate in low spots and in regions of low turbulence, since Water isheavier than the petroleum liquid.

It has been observed that internal corrosion of pipe lines is worstalong the bottom of the lines and in dips in the lines where water andscale particles settle. To prevent such corrosion it is desirable that arelatively high concentration of a suitable inhibitor be present atthese points where water and scale particles tend to accumulate. By andlarge it is not practical to accomplish this result merely by adding aninhibitor in conventional liquid or powdered form to the oil in thepipeline. If conventional oil soluble inhibitors are employed they wouldremain in the oil phase and would not pass into the water phase. Ifconventional water soluble inhibitors were added to the oil they wouldremain dispersed in the oil phase and would enter the separated waterphase only to a small extent if at all.

Thus it is an object of the present invention to provide a method forinhibiting internal corrosion in pipe lines in the areas in which waterand scale particles tend to settle out. It is a further object of theinvention to provide a method by which inhibitors can be introduced intoa pipe line and conducted to regions where moisture tends to accumulateto thereby prevent corrosion in such regions.

In accordance with this invention these objects are ac- 2,7955% PatentedJune Il, 1957 lying on the surface or near the surface of non-levelterrain.

Oil 3 is shown passing through the pipe line 1 together with addedpellets 4. In the regions A and C, water does not tend to settle out andaccumulate due to the fact that in these regions the line has either apositive or negative slope. However, in region B, constituting a naturalwater trap, water or moisture 2 tends to accumulate. Also in placeswhere the velocity of the fluid stream diminishes, as for example wherevalves, T-connections, etc. are inserted in the line, water may alsotend to settle out and accumulate. In addition, where the line is fairlylevel some water may settle out along the bottom of the pipe line. Inany of these areas the accumulated moisture tends to acceleratecorrosion.

In accordance with this invention corrosion in such areas is preventedby introducing into the pipe line pellets 4 of selected size and densityso that they will settle out in the same areas as does moisture and asdo scale particles. These pellets are composed of or contain corrosioninhibitors and are preferably slowly water soluble and oilinsoluble sothat they will resist disintegration for an appreciable length of timeuntil they finally settle into a region of accumulated water. Preferablyalso the pellets are of a range of densities and size so that while someof them will settle out at one particular point in the pipe line otherswill travel on to other particular settling points along thel ine. Insettling out in the same areas as those in which the water accumulatesthese pellets will slowly dissolve in the water and thus exert thedesired inhibiting action. Thus, in operation the oil insoluble pelletsare swept along with the oil flow in the pipe line. However, in regionB, a certain number of these pellets will settle out into the waterlayer and become dissolved therein, thus placing a high concentration ofinhibitor in a region where severe corrosion would otherwise occur.Other pellets will pass on through the pipe line to the next regionsimilar to region B, where water accumulates and some of those pelletswill settle out there, dissolve in the water, and exert their inhibitingaction. Thus by utilizing a plurality of pellets of a range of sizes anddensities it will be pos sible to send pellets through a section of pipeline to reach every area where water tends to accumulate.

As mentioned, the pellets are selected from a class ofcorrosion-inhibiting materials that are characterized by being solublein water and relatively insoluble in the hydrocarbon phase or oil phase.It is not essential that the pellets be completely water soluble sinceany insoluble components that might tend to block the pipe line as theyaccumulate would be removed during the conventional periodic scraperruns.

Satisfactory inhibitors that may be used include alkali metal nitritesand alkali metal chromates, e. g., sodium nitrite or sodium chromate.These inhibitors will function most satisfactorily in the absence ofreducing agents such as hydrogen sulfide. Thus they would be most usefulin lines handling fairly sweet crudes or petroleum products. In systemsin which appreciable quantities of hydrogen sulfide are present otherinhibitors are preferred. For example certain water-solubleurea-aldehyde type condensation products such as that known commerciallyas Uformite may be used. Other suitable inhibitors include certainquaternary ammonium salts such as a Cu; alkyl, trimethyl ammoniumchloride known commercially as Arquad S.

anoqpeo 1. eases the inhibitor materia itsel ma have oi fficientplasticity under pressure to enable it to act as its own binding agentin preparing the pellets. In other cases ix iarvb odi nt ma b eqoiro huext ih, o o odium s ate; o an o .numer usovo t et o Wat lu le adhe i emete e om h emp oyed as binding agents. Particularly desirable arebinding agents that render the pellets slowly water soluble to exe the rusefuilife L to e i disint ra io in t velling through the pipe line.Such materials as starch, hydrated magnesium silicate, sucrose; woodhour, or other cellulosic materials may also be used as fillers orextenders to prov de P per hs t Whe h eo vie re u r er o deo i on o idem h a e v lv he em- P ved i u obleom uot I i e ov rvdo r b t t s nh b oun e oe ta o o t hs house n oni o t n w h odi m oarbohat o o h a k m era o s t dju the p velue 8 o 9 o h g e i n dlz The de y o th .polle m varop eo lv u i i preferred that the density. of these added pellets begreater than the density of the hydrocarbon phase and equal to orgreater than the density of ,the water phase. A very desirable densityi. e., specific gravity, is in the range from 1.1 to 2.0. The specificgravity of some of the pellets may actually be as high as aboutSwhich'is of the order of magnitude of the specific grayities of twofrequently occurring corrosion products, ferrous sulfide and iron oxide.Thus some of the pellets would tend to settle out in the same areas asdo scale particles.

As to the size of thepelletsthis will depend tosomeextent on theconditions in the pipe line. In general, the pellets should be nosmaller. thanabout 0.05 inch in thicknesspr diameter and ingeneraltheyshould not be'larger than about 0.5 ineh. It is preferred thatpellets in the range of 0.1 to .25 inch beused; Preferably the charge ofp l et in roduc at aovoorti s t o in the p pe line eomprise anassortment of siz es so that some of them will settle out closer to thepoint of introduction than r ah u e nvvi h a p ural y of e s i 8- s nt av the am ie th r vw lzo .te oor f W11 to settle out in a given regionwhile others are carried along through the pipeline to a secondregion.

.It is not essential that the pelletsbe spherical in shape hsphe ovoid Kh? eh edre e l i fl to h carried a o mo tofiioiohflvth ou h he P eli toh e n o et n ho,P 1 .P P QK vnot he abrasive. in o r t s t t y willhottribute appreciably to the wear of pipe line pumps.

The number of pellets to be added at any particular part of the pipeline will depend on several factors including the volume of petroleumliquid being handled, the distance between stations, and so on. Thepellets can be added to the line most conveniently on the intake side ofthe pumps at eaeh'pnmping station along the line, either through astandpipe arrangement if there is some head on "theli alte side otthe'pump, or most simply by adding theiii to mean tank supplying thepump. The efiiciency of distribution of pellets through each section" ofthe line can'ibe assured by-adding "suflicient pellets at each pumpingstation so that a few will be carried to the receiving tank at the next'pumping station, as determined by sampling the incoming oil at thatpumping station.

It is to be understood that this invention is not to be limited to thespecific inhibitor compositions nor to any other specific featuresherein disclosed. It is intended th'at the scope Qfthis invention belimited only by the ap- Pe fQ ol m ,iyha im s:

1. An improved process for inhibiting internal corrosion in a pipe linetransporting hydrocarbon fluid containing small amounts of water whichcomprises introducing a plurality of solid pellets containing a watersoluble, oil insoluble corrosion inhibitor within the pipe line so t a.theoel i t a u d t ra e along with the fl i s Pel ets ev h de s eetethant hydrocarbon flu and e li ae as g ea a wat 'said p l a n athickness inlt he range from about0.05 to 0.5 inch.

j V 2. A process as defined in claim 1 in which the pellets have aspecific gravity in the range from 1.1 to 2 and a thickness in the rangeof 0.1 to 0.=25 inch.

3. Aiprooe esdefi e o i 1 in whi the .1 ra ity o pe ets ompr e ean e o tht Pe l a n differente zo a deh i e .R fiereho C t ih the. file 9f t i Plfi UNITED STATES .PATENTS 2,351,465 Wachter June 13, 1944 2,473,455Sorg' ..7 June '14, 1949 2,599,385 Gross et al June '3, '1952 2,636,000R'ohrbac k et a1 Apr. 21, 1953 2,6;84332 et al. Iune'20, 1 954

1. AN IMPROVED PROCESS FOR INHIBITING INTERNAL CORROSION IN A PIPE LINETRANSPORTING HYDROCARBON FLUID CONTAINING SMALL AMOUNTS OF WATER WHICHCOMPRISES INTRODUCING A PLURALITY OF SOLID PELLETS CONTAINING A WATERSOLUBLE, OIL INSOLUBLE CORROSION INHIBITOR WITHIN THE PIPE LINE SO THATTHE PELLETS ARE URGED TO TRAVEL ALONG WITH THE FLUID, SAID PELLETSHAVING A DENSITY GREATER THAN THE HYDROCARBON FLUID AND AT LEAST ASGREAT AS WATER, SAID PELLETS HAVING A THICKNESS IN THE RANGE FROM ABOUT0.05 TO 0.5 INCH.